Southern Russia remains affected by West Nile virus (WNV). In the current study, we identified the spatial determinants of WNV distribution in an area with endemic virus transmission, with special reference to the urban settings, by mapping probable points of human infection acquisition and points of virus detection in mosquitoes, ticks, birds, and mammals during 1999–2016. The suitability of thermal conditions for extrinsic virus replication was assessed based on the approach of degree-day summation and their changes were estimated by linear trend analysis. A generalized linear model was used to analyze the year-to-year variation of human cases versus thermal conditions. Environmental suitability was determined by ecological niche modelling using MaxEnt software. Human population density was used as an offset to correct for possible bias. Spatial analysis of virus detection in the environment showed significant contributions from surface temperature, altitude, and distance from water bodies. When indicators of location and mobility of the human population were included, the relative impact of factors changed, with roads becoming most important. When the points of probable human case infection were added, the percentage of leading factors changed only slightly. The urban environment significantly increased the epidemic potential of the territory and created quite favorable conditions for virus circulation. The private building sector with low-storey houses and garden plots located in the suburbs provided a connection between urban and rural transmission cycles.

The medical-geographical analysis of spatially heterogeneous distribution of tick-borne infections in the south of the Far East was provided. The cartographic analysis of the spread of infections was carried out on the basis of literary materials and statistical data of Rospotrebnadzor on the incidence of tick-borne diseases. Statistically significant spatial clusters with a high level of morbidity with different local confinement were identified. The high levels of morbidity were found in the south of the Khabarovsk Krai and the Jewish Autonomous Oblast for Siberian tick typhus, in the central part of the Khabarovsk Krai for tick-borne borreliosis, and in the southwest of the Zabajkalsky Krai for tick-borne encephalitis.

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